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      <h2><a href="./">Go by Example 中文版</a>: 协程</h2>
      
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            <p><em>协程(goroutine)</em> 是轻量级的执行线程。</p>

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            <a href="http://play.golang.org/p/8CNjga5cr6F"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
          <div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>

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          <div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
    <span class="s">&quot;fmt&quot;</span>
    <span class="s">&quot;time&quot;</span>
<span class="p">)</span>
</pre></div>

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          <div class="highlight"><pre><span class="kd">func</span> <span class="nx">f</span><span class="p">(</span><span class="nx">from</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
    <span class="k">for</span> <span class="nx">i</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">i</span> <span class="p">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">i</span><span class="o">++</span> <span class="p">{</span>
        <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">from</span><span class="p">,</span> <span class="s">&quot;:&quot;</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
    <span class="p">}</span>
<span class="p">}</span>
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          <div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
</pre></div>

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            <p>假设我们有一个函数叫做 <code>f(s)</code>。
我们一般会这样 <code>同步地</code> 调用它</p>

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          <div class="highlight"><pre>    <span class="nx">f</span><span class="p">(</span><span class="s">&quot;direct&quot;</span><span class="p">)</span>
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            <p>使用 <code>go f(s)</code> 在一个协程中调用这个函数。
这个新的 Go 协程将会 <code>并发地</code> 执行这个函数。</p>

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          <div class="highlight"><pre>    <span class="k">go</span> <span class="nx">f</span><span class="p">(</span><span class="s">&quot;goroutine&quot;</span><span class="p">)</span>
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            <p>你也可以为匿名函数启动一个协程。</p>

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          <div class="highlight"><pre>    <span class="k">go</span> <span class="kd">func</span><span class="p">(</span><span class="nx">msg</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
        <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">msg</span><span class="p">)</span>
    <span class="p">}(</span><span class="s">&quot;going&quot;</span><span class="p">)</span>
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            <p>现在两个协程在独立的协程中 <code>异步地</code> 运行，
然后等待两个协程完成（更好的方法是使用 <a href="waitgroups">WaitGroup</a>）。</p>

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          <div class="highlight"><pre>    <span class="nx">time</span><span class="p">.</span><span class="nx">Sleep</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;done&quot;</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>

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            <p>当我们运行这个程序时，首先会看到阻塞式调用的输出，然后是两个协程的交替输出。
这种交替的情况表示 Go runtime 是以并发的方式运行协程的。</p>

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          <div class="highlight"><pre><span class="gp">$</span> go run goroutines.go
<span class="go">direct : 0</span>
<span class="go">direct : 1</span>
<span class="go">direct : 2</span>
<span class="go">goroutine : 0</span>
<span class="go">going</span>
<span class="go">goroutine : 1</span>
<span class="go">goroutine : 2</span>
<span class="go">done</span>
</pre></div>

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            <p>接下来我们将学习协程的辅助特性：通道（channels）。</p>

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      <p class="next">
        下一个例子: <a href="channels">通道</a>
      </p>
      
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